Manufacturing process for finFET device

ABSTRACT

A method for fabricating a field effect transistor device includes removing a portion of a first semiconductor layer and a first insulator layer to expose a portion of a second semiconductor layer, wherein the second semiconductor layer is disposed on a second insulator layer, the first insulator layer is disposed on the second semiconductor layer, and the first semiconductor layer is disposed on the first insulator layer, removing portions of the first semiconductor layer to form a first fin disposed on the first insulator layer and removing portions of the second semiconductor layer to form a second fin disposed on the second insulator layer, and forming a first gate stack over a portion of the first fin and forming a second gate stack over a portion of the second fin.

DOMESTIC PRIORITY

This application is a continuation of U.S. patent application Ser. No.14/190,611, filed Feb. 26, 2014, which is a divisional application ofU.S. patent application Ser. No. 13/343,805, filed Jan. 5, 2012 (nowabandoned), the disclosure of which is incorporated by reference hereinin its entirety.

FIELD OF INVENTION

The present invention relates generally to field effect transistordevices, and more specifically, to finFET devices.

DESCRIPTION OF RELATED ART

Field effect transistor (FET) devices may be fabricated using fins thatmay define channel regions and source/drain and extensions of the FETdevice. Such finFET devices are often fabricated from a crystallinematerial such as, for example, silicon or germanium, that is disposed onan insulator layer. The crystalline material has a crystallineorientation that may be defined by Miller indices. The orientation ofthe fins relative to the crystalline orientation of the crystallinematerial, or the type of crystalline material used to fabricate the finsmay affect the performance of the devices depending on the type ofdevice that is fabricated. For example, nFET devices tend to havedesirable performance characteristics (e.g., mobility) when the fin isformed on a crystalline surface having a (100) orientation while pFETdevices tend to have desirable performance characteristics when formedon a surface having a (110) orientation. The use of different materials,regardless of crystalline orientation, may also result in desirableperformance characteristics for nFET and pFET devices.

BRIEF SUMMARY

According to one embodiment of the present invention, a method forfabricating a field effect transistor device includes removing a portionof a first semiconductor layer and a first insulator layer to expose aportion of a second semiconductor layer, wherein the secondsemiconductor layer is disposed on a second insulator layer, the firstinsulator layer is disposed on the second semiconductor layer, and thefirst semiconductor layer is disposed on the first insulator layer,removing portions of the first semiconductor layer to form a first findisposed on the first insulator layer and removing portions of thesecond semiconductor layer to form a second fin disposed on the secondinsulator layer, and forming a first gate stack over a portion of thefirst fin and forming a second gate stack over a portion of the secondfin.

According to another embodiment of the present invention, method forfabricating a field effect transistor device includes removing a portionof a first semiconductor layer and a first insulator layer to expose aportion of a second semiconductor layer, wherein the secondsemiconductor layer is disposed on a second insulator layer, the firstinsulator layer is disposed on the second semiconductor layer, and thefirst semiconductor layer is disposed on the first insulator layer,forming a spacer on a portion of the first semiconductor layer, adjacentto the first insulator layer, and the first semiconductor layer, growinga layer of epitaxial semiconductor material on exposed portions of thesecond semiconductor layer, removing portions of the first semiconductorlayer to form a first fin disposed on the first insulator layer, andremoving portions of the layer of epitaxial semiconductor material andthe second semiconductor layer to form a second fin disposed on thesecond insulator layer, and forming a first gate stack over a portion ofthe first fin and forming a second gate stack over a portion of thesecond fin.

According to yet another embodiment of the present invention, a fieldeffect transistor device includes a substrate, a first insulator layerdisposed on the substrate, a semiconductor layer disposed on the firstinsulator layer, a second insulator layer disposed on the semiconductorlayer, a first finFET device disposed on the first insulator layer, anda second finFET device disposed on the second insulator layer.

Additional features and advantages are realized through the techniquesof the present invention. Other embodiments and aspects of the inventionare described in detail herein and are considered a part of the claimedinvention. For a better understanding of the invention with theadvantages and the features, refer to the description and to thedrawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The subject matter which is regarded as the invention is particularlypointed out and distinctly claimed in the claims at the conclusion ofthe specification. The forgoing and other features, and advantages ofthe invention are apparent from the following detailed description takenin conjunction with the accompanying drawings in which:

FIGS. 1-6 illustrate an exemplary method for fabricating an exemplaryembodiment of a finFET device, in this regard:

FIG. 1 illustrates a side cut away view of a semiconductor on insulator(SOI) wafer;

FIG. 2 illustrates the resultant structure following the patterning of alithographic mask;

FIG. 3 illustrates the formation of a hardmask layer;

FIG. 4 illustrates the resultant structure following an etching process;

FIG. 5 illustrates a top view following the removal of the hardmasklayer and the patterning of a first gate stack and a second gate stack;and

FIG. 6 illustrates a side-cut away view along the line 6 of FIG. 5.

FIG. 7 illustrates an alternate exemplary embodiment of finFET devices.

FIGS. 8-9 illustrate an alternate fabrication method and resultantstructure for finFET devices, in this regard:

FIG. 8 illustrates a top view following the patterning of gate stacks;and

FIG. 9 illustrates a side cut away view along the line 9 of FIG. 8.

FIG. 10 illustrates an alternate exemplary embodiment of finFET devices.

FIGS. 11-13 illustrate an alternate fabrication method and resultantstructure of finFET devices, in this regard:

FIG. 11 illustrates the formation of a spacer;

FIG. 12 illustrates the epitaxial growth of semiconductor material; and

FIG. 13 illustrates the resultant structure following the patterning offins and gate stacks.

FIG. 14 illustrates an alternate embodiment of a resultant finFET devicewith a hardmask layer.

DETAILED DESCRIPTION

A finFET semiconductor device is a field effect transistor in which thebody of the field effect transistor that contains the channel is presentin a fin structure. As used herein, a “fin structure” refers to asemiconductor material, which is employed as the body of a semiconductordevice, in which the gate structure is positioned around the finstructure such that charge flows down the channel on the two sidewallsof the fin structure and optionally along the top surface of the finstructure.

It may be desirable to form finFET devices on a substrate that includedifferent materials or similar materials having different crystallineorientations used to form the fins. For example, it may be desirable toform an n-FET device with fins formed from a crystalline material, suchas, for example, Si, Ge, or SiGe having a (100) Miller indicesorientation, while it may be desirable to form a p-FET device with finsformed from a crystalline material having a different orientation, suchas, for example (110). Such orientations for the respective devices mayimprove the performance characteristics (e.g., charge mobility) of therespective devices. Alternatively, different types of semiconductormaterials, such as, for example, Si, Ge, SiGe or III-V type materialsmay be used to form finFET devices on a substrate, with or withoutconsideration of the crystalline orientation of the differentsemiconductor materials used for the respective devices. The methodsdescribed below include methods for fabricating finFET devices on asubstrate, where the fins are formed from similar materials havingdifferent crystalline orientations, from different materials, or fromdifferent materials having different crystalline orientations.

FIGS. 1-6 illustrate an exemplary method for fabricating an exemplaryembodiment of a finFET device. Referring to FIG. 1, a side cut away viewof a semiconductor on insulator (SOI) wafer 101 is shown that includes asubstrate layer 100 with a second insulator layer 102 disposed on thesubstrate layer 100. A second semiconductor layer 104 is disposed on thesecond insulator layer 102. A first insulator layer 106 is disposed onthe second semiconductor layer 104, and a first semiconductor layer 108is disposed on the first insulator layer 106. The substrate layer 100may include, for example, a silicon material. The first and secondinsulator layers 106 and 102 may include, for example, a buried oxide(BOX) or other insulating material such as, for example, silicon oxide,silicon nitride, silicon oxynitride, high-k materials, or anycombination of these materials. Examples of high-k materials include,but are not limited to, metal oxides such as hafnium oxide, hafniumsilicon oxide, hafnium silicon oxynitride, lanthanum oxide, lanthanumaluminum oxide, zirconium oxide, zirconium silicon oxide, zirconiumsilicon oxynitride, tantalum oxide, titanium oxide, barium strontiumtitanium oxide, barium titanium oxide, strontium titanium oxide, yttriumoxide, aluminum oxide, lead scandium tantalum oxide, and lead zincniobate.

The SOI wafer 101 may be formed utilizing standard processes includingfor example, SIMOX (separation by ion implantation of oxygen), waferbonding and layer transfer, or combination of those techniques. When alayer transfer process is employed, an optional thinning step may followthe bonding of two semiconductor wafers together. The optional thinningstep reduces the thickness of the semiconductor layer to a layer havinga thickness that is more desirable.

The second semiconductor layer 104 and the first semiconductor layer 108may include any type of semiconductor material such as, for example, Si,Ge, SiGe, type III-V materials, and/or type II-VI materials. The secondsemiconductor layer 104 and the first semiconductor layer 108 may besimilar materials having different crystalline orientations, differentmaterials having similar crystalline orientations, or differentmaterials having different crystalline orientations, or similarmaterials having similar crystalline orientations. In the illustratedexemplary embodiment, the second semiconductor layer 104 is formed froma semiconductor material having a (110) (using Miller index notation)crystalline orientation while the first semiconductor layer 108 isformed from a semiconductor material having a (100) crystallineorientation.

FIG. 2 illustrates the resultant structure following the patterning of alithographic mask 202 over a portion of the first semiconductor layer108. Following the patterning of the lithographic mask 202, exposedportions of the first semiconductor layer 108 and the first insulatorlayer 106 are removed using a suitable etching process. Suitable etchingprocesses may include, for example, a dry etching process, a reactiveion etching (RIE) process, or a wet etching process. The lithographicmask 202 may include a softmask material such as photoresist, a hardmaskmaterial such as silicon nitride, or a combination of softmask andhardmask.

FIG. 3 illustrates the formation of a hardmask layer 302 over exposedportions of the second semiconductor layer 104 and the firstsemiconductor layer 108. Once, the lithographic mask 202 (of FIG. 2) hasbeen removed, the hardmask layer 302 may be formed by, for example, aspin-on deposition, chemical vapor deposition (CVD), or plasma enhancedchemical vapor deposition (PECVD) process, and may include siliconnitride, silicon oxide, silicon oxynitride, amorphous carbon, or anysuitable combination of those materials. The hardmask layer 302 mayinclude a single layer of material or multiple layers of materials.Following the formation of the hardmask layer 302, a lithographic mask304 is patterned on portions of the hardmask layer 302. The exposedportions of the hardmask layer 302 may be removed by an etching processto expose portions of the second semiconductor layer 104 and the firstsemiconductor layer 108.

FIG. 4 illustrates the resultant structure following an etching processsuch as, for example, RIE or sidewall image transfer, that removesexposed portions of the second semiconductor layer 104 and the firstsemiconductor layer 108 (of FIG. 3) to pattern a second fin 404 and afirst fin 408, where the second fin 404 is disposed on the secondinsulator layer 102, and the first fin 408 is disposed on the firstinsulator layer 106.

FIG. 5 illustrates a top view following the removal of the hardmasklayer 302 (of FIG. 4) and the patterning of a second gate stack 501having a gate conductor 504 patterned over the second fin 404 and aportion of the second insulator layer 102, and a first gate stack 503having a gate conductor 502 patterned over the first fin 408 and aportion of the first insulator layer 106. In one embodiment, the firstfin 408 and the second fin 404 are substantially parallel. In oneembodiment, the first gate stack 503 and the second gate stack 501 areoriented in a substantially the same direction. Having all fins orientedin the same direction and all gates oriented in another same directiongreatly eases the device design and fabrication.

FIG. 6 illustrates a side-cut away view along the line 6 (of FIG. 5).The first and second gate stacks 501, 503 include a gate dielectriclayer 602 disposed on portions of the second fin 404 and first fin 408,respectively, and the gate conductor 502 and 504 is patterned on thedielectric layer 602. Although shown in FIG. 6 that the first and thesecond gate stacks have the same dielectric layer 602, it is alsoconceived that the first and the second gate stacks may have differentdielectric layer to achieve different device characteristics. The gateconductor 502 and 504 may comprise the same or different materials.

The gate dielectric may include silicon oxide, silicon nitride, siliconoxynitride, high-k materials, or any combination of these materials.Examples of high-k materials include but are not limited to metal oxidessuch as hafnium oxide, hafnium silicon oxide, hafnium siliconoxynitride, lanthanum oxide, lanthanum aluminum oxide, zirconium oxide,zirconium silicon oxide, zirconium silicon oxynitride, tantalum oxide,titanium oxide, barium strontium titanium oxide, barium titanium oxide,strontium titanium oxide, yttrium oxide, aluminum oxide, lead scandiumtantalum oxide, and lead zinc niobate. The high-k may further includedopants such as lanthanum, aluminum.

The gate conductor material may include polycrystalline or amorphoussilicon, germanium, silicon germanium, a metal (e.g., tungsten,titanium, tantalum, ruthenium, zirconium, cobalt, copper, aluminum,lead, platinum, tin, silver, gold), a conducting metallic compoundmaterial (e.g., tantalum nitride, titanium nitride, tungsten silicide,tungsten nitride, ruthenium oxide, cobalt silicide, nickel silicide),carbon nanotube, conductive carbon, or any suitable combination of thesematerials. The conductive material may further comprise dopants that areincorporated during or after deposition.

FIG. 7 illustrates an alternate exemplary embodiment, where followingthe deposition of the gate conductor material layer, and prior topatterning the gate stacks 501 and 503, a planarization process such as,for example, chemical mechanical polishing (CMP) is performed on thegate conductor material layer. Following the planarization process, thegate stacks 501 and 503 are patterned using, for example, a lithographicand etching process. The resultant structure includes gate stacks 503and 501 having substantially coplanar top surfaces 701 and 703.

Following the patterning of the gate stacks 501 and 503 as describedabove, spacers may be formed adjacent to the gate stacks 501 and 503 andover portions of the fins 404 and 408. Source/drain and extensions maybe formed in the exposed fins 404 and 408 by any suitable dopingprocess, such as, for example, ion implantation, gas phase doping,in-situ doped epitaxy growth, solid phase doping, plasma doping, and anysuitable combination of those techniques. The dopants may include anysuitable or desired n-type or p-type dopants or combination of dopants.The fins 404 and 408 may be doped with different types of dopants suchthat, for example, the fin 404 and gate stack 501 become a pFET device,while the fin 408 and gate stack 503 become an nFET device.Alternatively, the fin 404 and gate stack 501 become an nFET device,while the fin 408 and gate stack 503 become a pFET device. The differentdopants may be implanted using, for example, a succession of masking andimplantation processes, and/or an angled ion implantation process. In analternative embodiment, the fins 404 and 408 may be doped with sametypes of dopants but different amount of dopants such that both finFETshave the same device type but different device characteristics such asdifferent threshold voltages. In some embodiments, the portion of underthe gate stack may also be doped to adjust device characteristics.Neither, one, or both fins may be doped. Epitaxy growth (not shown) maybe performed to thicken fins in the source/drain to reduce source/drainresistance. Another purpose of the epitaxy growth may be to mergesource/drain of adjacent multiple finFETs to handle high electricalcurrent.

Following the ion implantation process, annealing and the formation of asilicide (not shown) over Source/drain and extensions of the devices maybe performed. A capping layer (not shown) and conductive contacts (notshown) may also be formed following salicidation (self-alignedsilicidation).

FIGS. 8-9 illustrate an alternate fabrication method and resultantstructure for finFET devices. In this regard, the methods describedabove in FIGS. 1-4 have been performed such that the fins 404 and 408with the hardmask layer 302 disposed on the fins 404 and 408 have beenformed. FIG. 8 illustrates a top view following the patterning of gatestacks 501 and 503 over portions of the second insulator layer 102 andthe first insulator layer 106, and the second fin 404 and the first fin408 respectively.

FIG. 9 illustrates a side cut away view along the line 9 (of FIG. 8).The dielectric layer 602 has been patterned over the second fin 404 andthe first fin 408, and the hardmask layer 302. The gate conductors 502and 504 have been patterned over the dielectric layer 602 in a similarmanner as described above.

FIG. 10 illustrates an alternate exemplary embodiment, where followingthe deposition of the gate conductor material layer, and prior topatterning the gate stacks 501 and 503, a planarization process such as,for example, chemical mechanical polishing (CMP) is performed on thegate conductor material layer. Following the planarization process, thegate stacks 501 and 503 are patterned using, for example, a lithographicand etching process. The resultant structure includes gate stacks 501and 503 having substantially coplanar top surfaces 701 and 703.

FIGS. 11-13 illustrate an alternate fabrication method and resultantstructure of finFET devices. In this regard, the methods described abovein FIGS. 1-2 have been performed. Referring to FIG. 11, following theremoval of portions of the first insulating layer 106 and the firstsemiconductor layer 108, a spacer 1102 is formed on the secondsemiconductor layer 104, adjacent to the first insulating layer 106, andthe first semiconductor layer 108. The spacer may include, for example,a nitride or oxide material, and may be formed by, for example, aconformal deposition process such as, a CVD, or PECVD, followed by anetching process, such as, an anisotropic etching process.

FIG. 12 illustrates the resultant structure following the epitaxialgrowth of semiconductor material 1202 that is seeded by exposed portionsof the second semiconductor layer 104. In the illustrated embodiment theepitaxially grown semiconductor material 1202 is a material similar tothe second semiconductor layer 104 and has a similar crystallineorientation.

FIG. 13 illustrates the resultant structure following the removal of thelithographic mask 202, the spacer 1102, and the hardmask layer 302 (notshown), and the patterning of the fins 404 and 408 and the gate stacks501 and 503 using similar methods as described above.

FIG. 14 illustrates an alternate embodiment of a resultant structurefollowing the removal of the lithographic mask 202 and the spacer 1102and the patterning of the fins 404 and 408 and the gate stacks 501 and503 using similar methods as described above, however the hardmask layer302 has not been removed prior to the patterning of the fins 404 and 408and the gate stacks 501 and 503.

Though the illustrated exemplary methods and embodiments described aboveillustrate the formation of two fins and gate stack arrangements, one ofordinary skill in the art would understand that any number of finFETdevices may be fabricated on each of the insulator layers 102 and 106using similar methods as described above.

The described exemplary methods and embodiments provide for finFETshaving fins with different materials and/or different crystallineorientations to be fabricated on an SOI wafer.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, element components,and/or groups thereof.

The corresponding structures, materials, acts, and equivalents of allmeans or step plus function elements in the claims below are intended toinclude any structure, material, or act for performing the function incombination with other claimed elements as specifically claimed. Thedescription of the present invention has been presented for purposes ofillustration and description, but is not intended to be exhaustive orlimited to the invention in the form disclosed. Many modifications andvariations will be apparent to those of ordinary skill in the artwithout departing from the scope and spirit of the invention. Theembodiment was chosen and described in order to best explain theprinciples of the invention and the practical application, and to enableothers of ordinary skill in the art to understand the invention forvarious embodiments with various modifications as are suited to theparticular use contemplated.

The diagrams depicted herein are just one example. There may be manyvariations to this diagram or the steps (or operations) describedtherein without departing from the spirit of the invention. Forinstance, the steps may be performed in a differing order or steps maybe added, deleted or modified. All of these variations are considered apart of the claimed invention.

While the preferred embodiment to the invention had been described, itwill be understood that those skilled in the art, both now and in thefuture, may make various improvements and enhancements which fall withinthe scope of the claims which follow. These claims should be construedto maintain the proper protection for the invention first described.

What is claimed is:
 1. A method for fabricating a field effecttransistor device, the method comprising: removing a portion of a firstsemiconductor layer and a first insulator layer to expose a portion of asecond semiconductor layer, wherein the second semiconductor layer isdisposed on a second insulator layer, the first insulator layer isdisposed on the second semiconductor layer, and the first semiconductorlayer is disposed on the first insulator layer; forming a spacer on atop surface of a portion only of the second semiconductor layer,adjacent to the first insulator layer, and the first semiconductorlayer; growing a layer of epitaxial semiconductor material on exposedportions of the second semiconductor layer; removing portions of thefirst semiconductor layer to form a first fin disposed on the firstinsulator layer, and removing portions of the layer of epitaxialsemiconductor material and the second semiconductor layer to form asecond fin disposed on the second insulator layer; and forming a firstgate stack over a portion of the first fin and forming a second gatestack over a portion of the second fin.
 2. The method of claim 1,wherein the removing portions of the first semiconductor layer to formthe first fin disposed on the first insulator layer and removingportions of the second semiconductor layer to form the second findisposed on the second insulator layer comprises: depositing a hardmasklayer over exposed portions of the first semiconductor layer and thesecond semiconductor layer; removing portions of the hardmask layer toexpose portions of the first semiconductor layer and the secondsemiconductor layer; and removing exposed portions of the firstsemiconductor layer and the second semiconductor layer.
 3. The method ofclaim 2, further comprising removing exposed portions of the hardmasklayer following the removing the exposed portions of the firstsemiconductor layer and the second semiconductor layer.
 4. The method ofclaim 1, wherein the forming the first gate stack over the portion ofthe first fin and forming the second gate stack over the portion of thesecond fin comprises: depositing a dielectric layer over exposedportions of the first insulator layer, the first fin, the secondinsulator layer, and the second fin; depositing a gate conductor layerover the dielectric layer; patterning a mask over portions of the gateconductor layer; and removing exposed portions of the gate conductorlayer and the dielectric layer.
 5. The method of claim 2, wherein theforming the first gate stack over the portion of the first fin andforming the second gate stack over the portion of the second fincomprises: depositing a dielectric layer over exposed portions of thefirst insulator layer, the first fin, the second insulator layer, thesecond fin, and the hardmask layer; depositing a gate conductor layerover the dielectric layer; patterning a mask over portions of the gateconductor layer; and removing exposed portions of the gate conductorlayer and the dielectric layer.
 6. The method of claim 4, furthercomprising performing a planarization process on the gate conductorlayer prior to patterning the mask over portions of the gate conductorlayer.
 7. The method of claim 5, further comprising performing aplanarization process on the gate conductor layer prior to patterningthe mask over portions of the gate conductor layer.
 8. The method ofclaim 1, further comprising: patterning a masking material over portionsof the first semiconductor layer prior to removing the portion of thefirst semiconductor layer and the first insulator layer; and removingthe masking material following growing the layer of epitaxialsemiconductor material.
 9. The method of claim 1, wherein the second finhas a top surface at a same level as a top surface of the first fin, andwherein the second fin comprises the second semiconductor layer and theepitaxial semiconductor material formed directly on the secondsemiconductor layer.